1. Field of the Invention
The present invention generally relates to a method and system of controlling tape drives within a tape drive library where a backup server utilizes client backup schedules and pending client restore requests to efficiently control the powering on and off of tape drives within a tape drive library.
2. Description of the Related Art
Tape libraries according to prior art include a plurality storage slots with or without tape cartridges, one or more robots for transporting tape cartridges from slots to drives and a plurality of tape drives. A tape drive library such as IBM™ TS3500 can include up to 192 Linear Tape Open (LTO) or IBM™ TS1120 drives.
The tape drives included in a tape drive library in addition to tape drives in a standalone configuration are generally not utilized every minute or hour of the day. Tape drives are usually used for backup or restore functions. Many customers perform one or two backups per day for every client and data restores happen infrequently and are sporadic. In addition some tape drives might be used for other activities such as media-conditioning or space-reclamation. Even with all these functions taking place on the installed tape drives, a tape drive is never utilized 100% on each day of the week. Thus, tape drives have much idle time when they are not working during many periods of the day. Over certain periods, such as weekends, the non-utilization period may be even longer. FIGS. 1A and 1B give an example of tape drive utilization of a typical customer environment.
According to the utilization charts in FIGS. 1A and 1B, it can be seen that several drives might not be needed during several hours of a day. These tape drives are powered on and consuming power while not involved in any data recording or restoring function. A single tape drive according to a representative specification consumes between 125 to 130 W (at 0.5 A, and 250-260V). An operational drive unused in a tape drive library for 24 hours it will consume approximately 3 KWh, (calculated at 125 W), that is equivalent to creating 1.98 Kg of CO2. Additionally, a large number of tape drives typically installed in a commercial tape drive library are provided in anticipation of a major disaster where large amounts of data must be restored over a short period of time to meet defined Recovery Time Objective (RTO). Thus, the number of tape drives typically installed in a tape drive library system for a backup solution is the number of drives required for daily backup operations.
Tape drives and tape libraries are typically part of backup solutions shown in the client server backup architecture of FIG. 2.
Multiple backup clients 102 are connected to a network 106, which connects them to backup server 107. Backup server 107 is connected to the tape drive library and drives 110 via network 120. Additionally, backup server 107 is connected to the tape drive library 110 via a management network 118. The networks 106, 118 and 120 might be different networks as shown or it might also be one and the same network. These networks may be based on Ethernet and the Transmission Control Protocol and Internet Protocol (TCP/IP) or on a different type of network such as fibre channel with the Small Computer System Interface (SCSI) or Fibre Channel over Internet Protocol (FCIP).
The backup clients 102 include data to be backed up which is stored on file systems 108. Furthermore the backup clients 102 include backup client software which sends the files for backup 112 from the local file system 108 to the server 107.
The backup server 107 is a software application running on a computer system. The backup server 107 stores, or backups 112 the files sent by the backup client 102 on tape drive library 110.
One example for a backup server is IBM™ Tivoli Storage Manager™ which also provides backup clients for different purposes such as file system backup or database backup.
The backup process 112 is defined as the clients 102 sending the files to the server 107. This process is usually triggered by predetermined schedules defined by an administrator within the server 107. Thus, the backup server 107 has knowledge of the client 102 backup schedules. These schedules are executed automatically and can be planned efficiently to avoid having to many clients 102 backing up data to the server 107 at the same time. A backup schedule usually contains information about a client name, the number of sessions, a start date and start time. Backup schedules are stored in the server 107, for example, in a database which the server 107 uses to store the schedule information. When a backup process 112 starts, the backup server 107 also selects the appropriate storage medium and tape drive 110 for that particular backup operation.
The restore process 114 is usually initiated by the backup client 102 having the need to retrieve data from the server 107 which has been lost in the local file system 108. During the restore process 114, the backup client 102 requests the data from the backup server 107. The data is usually denoted by names representing file names. The backup server 107 keeps a local database where it stores the data referenced by the names. The backup server 107 uses this database to locate the data requested by the client 102 and send or restore 114 this data to the client 102. The backup client 102 then stores the files in the appropriate directories of the local file system 108.
Based on the backup solution according to prior art, (FIG. 2), it becomes obvious that the backup server 107 has specific knowledge about the client 102 backup schedules. This information is used in the present invention to efficiently control the powering on and off of tape drives.
The fact that tape drives are not utilized 100% during the day makes it necessary to implement power saving techniques where tape drives are only powered on as they are needed. Powering on a tape drive takes usually between 60 to 120 seconds, and mounting a tape usually takes between 30 to 60 seconds. Thus, the additional time required to power on a tape drive has only a medium impact to the overall backup 112 or restore 114 operations. The present invention anticipates that the tape drives may be powered on before the backup processed 114 starts by utilizing the backup schedules stored in the backup server. This means that controlling the powering off and on of tape drives may not have any impact to the backup operation.
Tape drives according to prior art, such as the IBM™ TS1120 tape drive, implements power saving methods whereby the tape drive enters a power saving mode when it has not been used for a predetermined period of time. This method has a critical drawback in that it is independent of any backup and restore operation, leading to inefficient power saving cycles. More precisely, the tape drive itself does not know when a backup function scheduled to start, and it does not know when it is selected by the backup server. It may occur that the tape drive enters a power saving mode after a predetermined period of time, wherein immediately thereafter, it must power on again because the server has selected it for a backup or restore operation. This is inefficient. However, the present invention utilizes the knowledge of the backup server about the client backup schedules and pending client restore requests to efficiently control powering on and off tape drives within a tape drive library.